Felt product and process



Aug. 6, 1957 P. S. HESS Y FELT PRODUCT AND PROCESS Filed Jan. 7, 1955 Jamsm .5mm

INVENTOR.

PAUL S HESS j ATTORNEY United States Patent Oilice o 2,801,937 Patented Aug.V 6, 1957 2,801,937 VFELT PRODUCT AND PROCESS Paul S. Hess, West Orange, N. J., assignor to Congoleum- Nairn Inc., Kearny, N. J., a corporation of New York This invention relates to improved felt products suitable for use in the oor and wall covering industry as Well as to new processes for preparing such products.

In the floor and wall covering industry, it is frequently desirable to provide a backing material for certain compositions such as linoleum, plastic, rubber, and the like. Felted cellulosio bers impregnated with bituminous material, particularly asphalt, have long been used for this purpose. The same type of material is used as a base on which to print the design and wear layer of enamel surface oor and wall coverings. It is sometimes used by itself as an underlayment for other surface coverings and in building construction for rooting and siding.

Floor covering felt is` made on conventional paper making equipment of the Fourdrinier or cylinder type, although many of `the processing refinements necessary to provide good paper are not necessary when felting bers. As with paper, the fibers tained from rags, wood pulp, corrugated boxes, newspaper or the like and mixtures of them. The particular combination used to prepare a given felt is called the furnishj and in general, a furnish `which has a high rag content provides superior Hoor covering felt in regard to strength and flexibility. Typical furnishes comprise: 80% clean cotton rags, 10% other rags and 10% corrugated boxes; 50% paper, 50% woodpulp; 20% cotton rags, 40% newsprint, 40% wood pulp; 100% rag, and the like.

Floor covering felt generally must be -at least about 0.025 inch thick while the: thickness of `paper is usually only a fraction of that.` Floor covering felt rarely ex.` ceeds 0.10 inch and averages about 0.045 inch.V The density of floor covering feltis considerably less than that of paper. Because of the thickness required and because of economic considerations, it has been irnpractical to work with a felt having a density greater than that reected by a gauge to weight ratio of 0.8 measured according to the formula:

l Thickness offen (inches) 1000 Weight of 480 Vsquare feet of felt (pounds) where the lower values represent the higher densities. Frequently felt will have a gauge `to weight ratio as high as 1.2 but in general, it averages about 1.0. Paper usually has a gauge to weight ratio considerably below 0.8. At the densities referred to, felt does not have the strength of good paper nor the strength which is required for use in the floor covering industry. It has been the practice, therefore, to supplement the felt by impregnating it as aforementioned with a bituminous' material such as asphalt.

The bitumen absorption ability of certain felt is a further identifying characteristic of floor covering felts. While it varies depending on the density of the felt and the kind and quality of the furnish employed, it usually ranges from about 80% to about 140% of the bone dry weight ofthe felt, although that amount is not always employed may be ob-` stoving bitumen impregnated felt.

Numerous bituminous materials are conventional for use asY described above but usually asphalts of either petroleum or naturall origin or blends of both are used. They may be crude, blown or steam distilled. In addition, other bituminous materials may be used such as tar or pitch residues of vegetable and animal origin.' Generally, the bitumen most suitable for impregnating a felt base sheet will have a melting point of about F. to about F.; a penetration of about 8 to about 12 at 32 F.; a penetration of about 22 to about 27 at77 F.; a penetration of about 95 to about 100 at 115 F.; and a ductility of not less than 20 at 77 F. when tested according to A. S. T. M. methods E28-51T, D5-49, and DHS-44.

The quality of bitumen impregnated felt is measured in terms of flexibility (the extent to which the product may be bent before it breaks or cracks), stiiness (the amount of force which must be applied to bend the product) and strength. Other properties are also important, particularly ability to resist migration ofthe bituminous material into any adjoining wear layer which may be present, resistance to moisture and alkali, dimensional stability, and the like. The latter properties referred to are reflected in the use of a product after in-` stallation, and it is common practice to treat impregnated felt in regard to them. For example, most impregnated felt products are coated with one or more oleoresinous or resinous seal coats before a wear layer such as linoleum or print paint is applied in order Vto minimize bitumen migration. The former propertiesare most evident in processing, handling and installation.,

The felt must be strong enough to support a wear layer during.. processing, particularly where large portions of the combined wear layer and felt must be suspended, as in stoving. Burstngstrength forces` are also important. Additives are sometimes used in conjunction with bitumen to improve the strength of a product.

Flexibility governs many of the uses to which a finished oor covering may beV put. Frequently, however, the flexibility of the wear layer is less than that of the saturated felt backing, Stillness, on the other hand, has proved to be extremely important to the installation of saturated felt backed floor coverings, especially in the form of sheet goods. Main` be expendedin bending a composite of a backing and a.

wear layer and frequently it is more than additive.

The use of bituminous materials as impregnants for felt gives rise to a special stiitness problem in connection with tloor covering of the linoleum or printed felt base type. subjected to elevated temperatures on the order of from 110 F. to 190 F. for from 10 to 30 days after it has been worked into sheets and laminated to a felt backing so as to cure the composition by eiecting continued oxidation and/or polymerization thereof. Printed felt base must also be subjected to high temperatures of from F. to 190 F. for from 24 to 96 hours to eifect drying of the printed, paint wear layer. Stoving, as described above, greatly increases the stiffness of impregpolymerization of the bituminousmaterial.4

It is an object of this invention to prevent or greatly.`

decrease the amount of stiffness increase which occurs in The stiffness of irnpregnated felt also increases with time under normal storand resistance to shearing.

and in those cases, it is not critical.-`

As is` well known in the art, linoleum must be:

age conditions whether it has been stoved or not, and it is a further object of the invention to eliminate or minimize this increase. Once impregnated felt backed products have been permanently installed, increased stifness is not a problem; however, printed felt base products are not customarily permanently atxed to a surface and thus, to a lesser extent, it is an object of the invention to prevent or minimize any increase in stiffness in these products with time after installation. The aforementioned and other objects will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawing in which:

Fig. l is a diagrammatic side elevational View illustrating a method for impregnating felt in accordance with the invention.

Fig. 2 is a cross-sectional view of felted cellulosic bres in sheet form impregnated in accordance with the invention.

It has now been discovered that the incorporation of relatively small amounts of polypropylene or polybutylene glycol or mixtures of them into bitumen saturated felt results in a greatly improved product and achieves the above and other objects.V

Only very small amounts of the above glycols are needed to achieve marked differences in stiffness properties. About 0.05% by weight based on the bone dry weight of the felt is satisfactory for some purposes while from about 1.5% to about 2% is preferred not only because it provides the maximum improvement but because it is easier to control the application of the larger amount. Although up to 12% of the glycol may be employed without giving rise to any appreciable deleterious effects in the saturated felt, it is generally uneconomical to employ more than about 3% because the quality improvement gained thereby is not great, and the felt loses some of its ability to adhere well to the kinds of adhesive ordinarily used for installation. Above 12% the saturated felt begins to lose strength.

To demonstrate the improved results obtained by the practice of the invention, the data tabulated in Table l were assembled. The stiffness of the felt was measured in Suvant units, which are arbitrary units of stiffness determined from the Suvant apparatus as manufactured by the Taber Instrument Company of North Tonawanda, New York, and of the type described in their bulletin AV-5 entitled The Suvant for Testing Paper and U. S. Patent No. 2,063,275. Bach unit represents a 3 gram load applied to a 7.5 cm. test length (1.5 inches wide) and the reading from the apparatus is recorded when the test sample is deflected 22.5 degrees.

All the samples identified in Table 1 comprised felt prepared by the cylinder process from a furnish of 42% rags and 58% wood pulp. The felt was impregnated with asphalt to 56% of the bone dry weight of the felt and was stoved at 180 F. for 30 days. Suvant measurements were taken immediately prior to stoving, immediately after stoving, and after six months storage under atmospheric conditions dating from the completion of stoving. Samples 4 and 5 have been included to demonstrate the particular efectiveness of polypropylene glycol in contrast to other polyhydric materials which might be expected to be eifective in view of the present invention.

Table 1 Suvant Reading (Warp Direction) Sample No. Amount of Additive Before After Six Stoving Stoving Months Storage Control-% 165 225 250 1% Polypropylene Glycol. 120 120 120 2% Polypropylene GlycoL 115 115 115 5% Polyethylene Glycol- 165 215 240 5% Glycerine 130 225 250 Dimensional stability, as aforementioned, is also an important characteristic of impregnated felt. Improvements in this regard are achieved by employment of the present invention. Many oor covering products, and particularly linoleum, tend to expand after installation. Such expansion is evidenced by a raising of the linoleum in the area of butted seams. When two sheets of butted material so expand, there appears to be a tent along the seam and thus the phenomenon is called tenting A measurement of the dimensional stability of impregnated felt which is not laminated to another composition is of little practical Value. A good test comprises preparing a control sample of impregnated felt backed linoleum and a test sample of impregnated felt backed linoleum having polypropylene and/or polybutylene glycol incorporated therein. Samples measuring 8 inches by 8 inches are dried at F. fr four hours and then placed in a dessicator for three days. The samples are scribed with a 61/2 inch trammel in the weft direction and placed felt side down in Contact with a water saturated felt pad. Contact is assured by placing one inch strips of waterproof material around the samples to form a dam. The total linear distance of the cut made by the trammel is measured at prescribed time intervals to determine the amount of growth that occurs. Table 2 sets forth the results of this test in which felt of the type described in connection with Table 1 was employed.

Table 2 Amount of Increase in Linear Impregnated Felt Polypropy- Measurement (Inches) Backed Linoleum lene Glycol Sample (Percent of Bone Dry 1 Hr. 3 Hr. 24 Hr.

Felt) In order to achieve the greatly improved results set forth in the above two tables, it has been discovered that the polypropylene and/or polybutylene glycol must be, for the most part, water insoluble and therefore it is preferred that it have a molecular weight of over about 2000. The reason for this is not known; however, a substantially completely water soluble polypropylene and/or polybutylene glycol has little or no effect on the stiifness characteristics or the dimensional stability of bitumen impregnated felt. On the other hand, it appears that the very high molecular weight polypropylene and/ or polybutylene glycols, or those being only very slightly water soluble, may be used in the invention, there being only minor differences resulting from increased molecular weight. V

The glycol may be applied to the felt in a number of Ways. It may be added in the beater stage of preparation of the felt. It may be incorporated in the bituminous material prior to impregnation. It is preferred, how ever, that it be added from a water emulsion by dipping or coating the bitumen impregnated felt. The latter process is easy to control and has a salutary effect on the practical application of the invention. It has been discovered that the advantages to be obtained by use of the glycols in the manner set forth herein are not achieved unless there is a small amount of moisture in therfelt. The equilibrium moisture content of most bitumen saturated or impregnated felt is about 4%, and this amount is sutlicient. However, the moisture content of felt immediately after preparation in the conventional manner and of bitumen impregnated felt immediately after stoving is about 0%, both products requiring about 24 hours under normal storage conditions to achieve their equilibrium'moisture content. In the practice of the preferred process of the invention, saturated felt is coated with or dipped in a water emulsion of polypropylene and/or polybutylene glycol, and a small amount of the moisture therefrom is retained in the felt along with the glycol during the addition of a wear layer and stoving. Apparently the well-known humectant property of some glycols contributes to this phenomenon. In any event, it is an important advantage in that the desired properties of the felt are evident immediately after stoving. When the glycol is added from a solvent prior to stoving, the felt does not achieve the desired properties until it has reached a moisture content in the neighborhood of the equilibrium moisture content.

An excellent emulsion for use in the present invention employs:

Parts Polypropylene glycol 40 Water 60 Emulsifyng agents 1 1 Many similar formulations will immediately become apparent to those skilled in the art, depending on the amount of glycol which is desired to be added, the speed of operation, the type of felt, the type of saturant, and the like. The emulsion described above permits uniform glycol addition at the preferred levels of 1.5%-2% and at relatively high speeds for most saturated felts. Any emulsifying agent which provides a uniform dispersion of the glycols in water may be used. A mixture of polypropylene glycol monolaurate and ammonium hydroxide has proved successful, as well as stearic acid and morpholine.

While the above invention has been described in connection with various specic illustrative examples, it is not to be limited thereto. Many modifications and variations will be apparent to those skilled in the art, and reference is to be had to the appended claims for a delinition of the limits of the invention.

What is claimed is:

1. Felted cellulosic bers in sheet form, said sheet having a thickness of at least about 0.025 inch and less than about 0.10 inch and a gauge to weight ratio measured by the formula Felt thickness (inches) X100() Weight of 480 square feet of felt (pounds) within the range of from about 0.8 to about 1.2, said sheet having uniformly dispersed therein from about 25% to about 140% (by weight of the bone dry felt) of a bituminous impregnant and a substantially water insoluble polymerized glycol having a molecular weight of at least about 2000, selected from the group consisting of polypropylene glycol and polybutylene glycol said polymerized glycol being present in an amount not more than 12% by weight of the bone dry felt.

2. A product according to claim 1 wherein said polymerized glycol is present in an amount not more than 3% by weight of the bone dry felt.

3. A product according to claim 1 wherein the bituminous impregnant is asphalt and wherein the polymerized gylcol content is from about 1.5 to about 2%.

6 4. In a process for preparing felted cellulosic bers by depositing a slurry of loose cellulose fibers on a base in the form of a sheet and removing the moisture therefrom to provide a dry sheet having a thickness of at least about 0.025 inch and less than about 0.10 inch and a gauge to weight ratio measured by the formula Felt thickness (inches) X() Weight of 480 square feet of felt (pounds) of from about 0.8 to about 1.2, followed by impregnating the sheet with from about 25% to about 140% (based on the bone dry weight of the sheet) of a bituminous impregnant, the improvement which comprises incorporating into the felted bers up to about 12% of a substantially water insoluble polymerized glycol having a molecular weight of at least about 2000, selected from the group consisting of polypropylene glycol and polybutylene g1yco1.-

5. A process according to claim 4 wherein from about 1.5% to about 2% of the polymerized glycol is added to the dry sheet from aqueous suspension.

6. A process according to claim 4 wherein the bituminous impregnant is asphalt and wherein the amount of polymerized glycol does not exceed about 3%, the same being added to the asphalt impregnated sheet by dipping the sheet in an aqueous suspension of the polymerized glycol.

7. A product according to claim 1 wherein the polymerized glycol is polypropylene glycol.

8. A product according to claim 1 wherein the amount of bituminous impregnant is from about 80% to about by weight of the bone dry felt.

9. A product according to claim 2 wherein the polymerized glycol is polypropylene glycol.

l0. A process according to claim 4, wherein the polymerized glycol is polypropylene glycol.

1l. Felted cellulosic fibers in sheet form, said sheet having a thickness of at least about 0.025 inch and less than about 0.10 inch and a gauge to weight ratio measured by the formula Felt thickness (inches) X 1000 Weight of 480 square feet of felt (pounds) References Cited in the le of this patent UNITED STATES PATENTS 1,610,959 Lines Dec. 14, 1926 2,568,849 Fasold Sept. 25, 1951 2,629,674 Bricks Feb. 24, 1953 

1. FELTED CELLULOSIC FIBERS IN SHEET FORM, SAID SHEET HAVING A THICKNESS OF AT LEAST ABOUT 0.025 INCH AND LESS THAN ABOUT 0.10 INCH AND A GAUGE TO WEIGHT RATIO MEANSURED BY THE FORMULA 